PE2950, LSI SAS -> SATA very slow

Tino Schwarze linux-poweredge.lists at tisc.de
Tue May 4 03:58:58 CDT 2010


On Tue, May 04, 2010 at 10:32:25AM +1000, Adam Nielsen wrote:
> > 10MB/sec does seem extremely poor. we've had read slowness when Linux block
> > device read-ahead was too small. Once properly configured, performance on
> > RAID-5 went from 150MB/sec to 500MB/sec, so the difference is dramatic. we
> > usually tune read-ahead (in Linux) buffers starting from 8MB to 32MB and
> > benchmark to see what works best. but your problem may be elsewhere... we've
> > never seen 10MB/sec...
> 
> Have you got any pointers to where this can be adjusted?  It seems 
> (according to Google) there are countless methods and patches, most of 
> which are for rather old kernel versions.

man blockdev
blockdev --setra blocks /dev/sda

It is part of util-linux-ng .

HTH,

Tino.

-- 
"What we nourish flourishes." - "Was wir nähren erblüht."

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